Spinach is rich in the antioxidant lutein, which is thought to help protect against cognitive decline, according to researchers from Tufts University. And a longitudinal study at Harvard Medical School found that women who reported eating the most leafy green and cruciferous vegetables had a markedly lower rate of cognitive decline, compared to those who ate the least.
It is incredibly easy to abuse and become addicted to methylphenidate, and misuse is shockingly prevalent, even among so-called “non-affected” users: with students, biohackers, soccer moms and busy executives popping it – and many of the other smart drugs below – like candy. It’s also not all it’s cracked up to be. Side effects include insomnia, stomach ache, headache and anorexia. Overdoses (which may occur easily as it can be difficult to estimate and regulate dosage) can lead to agitation, hallucinations, psychosis, lethargy, seizures, tachycardia (rapid heart rate), dysrhythmia (irregular heart rhythms), hypertension and hyperthermia. Methylphenidate is particularly hazardous to developing brains, especially those of younger students who are frequently prescribed the drug or who – often in high school and college – use it without a prescription. The prefrontal cortex, located behind the forehead, is responsible for cognition, personality-expression and decision-making, and develops well into the mid-20s, at which point it takes over as the “rational” part of the brain. In the central nervous system, and particularly in the prefrontal cortex, dopamine levels must have a natural rise and fall in order for healthy rational processes (executive control) to develop. By influencing dopamine levels, methylphenidate can negatively impact this healthy cognitive development, especially when it is abused or used too frequently.
The blood half-life is 12-36 hours; hence two or three days ought to be enough to build up and wash out. A week-long block is reasonable since that gives 5 days for effects to manifest, although month-long blocks would not be a bad choice either. (I prefer blocks which fit in round periods because it makes self-experiments easier to run if the blocks fit in normal time-cycles like day/week/month. The most useless self-experiment is the one abandoned halfway.)

Next generation medical imaging and genomic sequencing studies, including my own work, have helped reveal that some foods are neuro-protective, literally shielding the brain from harm and supporting cognitive fitness over the course of a lifetime. Conversely, other foods are harmful for the brain, slowing us down in general, making us feel sluggish and tired, while at the same time increasing our risk of dementia.
Your brain loves omega-3 fatty acids, which are thought to play an important role in cognitive function. According to the New York Times describing research in the journal Neurology, low levels of these unsaturated fats in the blood are linked with smaller brain volume and worse performance on certain tests of mental function. Omega-3s, which are found in salmon and other cold-water fish like tuna, may improve the retention of brain cells and also bolster the brainpower of younger adults. According to University of Pittsburgh research published last year, adults under age 25 who increased their omega-3 intake over six months improved their scores on tests measuring working memory.
By analyzing the brain images, the team found that these patients, compared with people who weren’t susceptible to the placebo, had a difference in volume between the right and left sides of the limbic system in the brain, which is involved in instinct and mood. There were also differences in the number of nerve cell connections between the prefrontal cortex and other brain areas. Personality questionnaires revealed that these people had a higher self-awareness and openness than nonresponders.
The Neurohacker Collective is a group of scientists, academics, and creatives who, among other things, sell nootropics. One of its premier products is Qualia Original Stack (OS), which has 41 ingredients. The large print says it improves focus, mood, and energy within 30 minutes and “supports long-term brain health.” A 22-dose supply costs $129. Such stacks operate on the idea that synergies among ingredients yield additional benefits.
My worry about the MP variable is that, plausible or not, it does seem relatively weak against manipulation; other variables I could look at, like arbtt window-tracking of how I spend my computer time, # or size of edits to my files, or spaced repetition performance, would be harder to manipulate. If it’s all due to MP, then if I remove the MP and LLLT variables, and summarize all the other variables with factor analysis into 2 or 3 variables, then I should see no increases in them when I put LLLT back in and look for a correlation between the factors & LLLT with a multivariate regression.
For illustration, consider amphetamines, Ritalin, and modafinil, all of which have been proposed as cognitive enhancers of attention. These drugs exhibit some positive effects on cognition, especially among individuals with lower baseline abilities. However, individuals of normal or above-average cognitive ability often show negligible improvements or even decrements in performance following drug treatment (for details, see de Jongh, Bolt, Schermer, & Olivier, 2008). For instance, Randall, Shneerson, and File (2005) found that modafinil improved performance only among individuals with lower IQ, not among those with higher IQ. [See also Finke et al 2010 on visual attention.] Farah, Haimm, Sankoorikal, & Chatterjee 2009 found a similar nonlinear relationship of dose to response for amphetamines in a remote-associates task, with low-performing individuals showing enhanced performance but high-performing individuals showing reduced performance. Such ∩-shaped dose-response curves are quite common (see Cools & Robbins, 2004)
There are many studies that suggest that Creatine helps in treating cognitive decline in individuals when combined with other therapies. It also helps people suffering from Parkinsons and Huntingtons disease. Though there are minimal side effects associated with creatine, pretty much like any nootropic, it is not  absolutely free of side-effects. An overdose of creatine can lead to gastrointestinal issues, weight gain, stress and anxiety.
Qualia: Like TianChi, the nootropic blend Qualia is a “shotgun” approach, providing over forty-two different ingredients, including a host of herbal adaptogens, brain vitamins, amino acids, choline donors, anti-inflammatories and antioxidants too long to list here (you can view the full ingredient profile here). Unlike TianChi, it also contains synthetic nootropic “noopept”, which has about 1,000 times the potency of piracetam, along with a few other helpful ingredients, including curcumin and bioperine, and slightly higher amounts of caffeine. It also requires two daily dosing protocols: with the first dose taken on an empty stomach and the second with a meal (for those compounds better absorbed with food). For those who prefer to skip on the synthetic nootropic, get most of the compounds at slightly lower price point (Qualia is admittedly quite expensive at $150 for the two dosing bottles), and also get the addition of the Indian plant you learned about earlier called “Celastrus paniculatus”, there is a very similar supplement made by the same manufacturer called “Qualia Mind”.
A pastor named John Piper said it well, “If hearing about God’s judgment makes it harder for us to love God, then probably the God we love is a figment of our imagination and not the real and true God. If we would love the true God, we must know the true God. There is something wrong with our faith if we cannot sing praises to God not only as our loving Father but also as the righteous Judge of all the earth.”
"They're not regulated by the FDA like other drugs, so safety testing isn't required," Kerl says. What's more, you can't always be sure that what's on the ingredient label is actually in the product. Keep in mind, too, that those that contain water-soluble vitamins like B and C, she adds, aren't going to help you if you're already getting enough of those vitamins through diet. "If your body is getting more than you need, you're just going to pee out the excess," she says. "You're paying a lot of money for these supplements; maybe just have orange juice."

Nootropics may seem attractive to anyone who wants to try to improve their cognitive function and is willing to purchase powders, pills and other forms of these natural and synthetic supplements. Nootropic users have their own terminology, referring to measured combinations of nootropics and vitamins and minerals as “stacks.” For instance, Danger and Play, a site for active people, features a stack for beginners.[5] The recipe includes 1600 mg of the piracetam along with recommended dosages of supplements such as ALCAR, rhodiola and magnesium. There are recipes for morning, afternoon and night, thus providing daylong guidance on how to most effectively stack for more energy, greater concentration, and improved information retention. The stack tip specifically states that the ingredients are not addictive, especially if taken in strict accordance with the recipe.
Cytisine is not known as a stimulant and I’m not addicted to nicotine, so why give it a try? Nicotine is one of the more effective stimulants available, and it’s odd how few nicotine analogues or nicotinic agonists there are available; nicotine has a few flaws like short half-life and increasing blood pressure, so I would be interested in a replacement. The nicotine metabolite cotinine, in the human studies available, looks intriguing and potentially better, but I have been unable to find a source for it. One of the few relevant drugs which I can obtain is cytisine, from Ceretropic, at 2x1.5mg doses. There are not many anecdotal reports on cytisine, but at least a few suggest somewhat comparable effects with nicotine, so I gave it a try.
Another prescription stimulant medication, modafinil (known by the brand name Provigil), is usually prescribed to patients suffering from narcolepsy and shift-work sleep disorder, but it might turn out to have broader applications. “We have conducted at the University of Cambridge double-blind, placebo-controlled studies in healthy people using modafinil and have found improvements in cognition, including in working memory,” Sahakian says. However, she doesn’t think everyone should start using the drug off-label. “There are no long-term safety and efficacy studies of modafinil in healthy people, and so it is unclear what the risks might be.”
Analyzing the results is a little tricky because I was simultaneously running the first magnesium citrate self-experiment, which turned out to cause a quite complex result which looks like a gradually-accumulating overdose negating an initial benefit for net harm, and also toying with LLLT, which turned out to have a strong correlation with benefits. So for the potential small Noopept effect to not be swamped, I need to include those in the analysis. I designed the experiment to try to find the best dose level, so I want to look at an average Noopept effect but also the estimated effect at each dose size in case some are negative (especially in the case of 5-pills/60mg); I included the pilot experiment data as 10mg doses since they were also blind & randomized. Finally, missingness affects analysis: because not every variable is recorded for each date (what was the value of the variable for the blind randomized magnesium citrate before and after I finished that experiment? what value do you assign the Magtein variable before I bought it and after I used it all up?), just running a linear regression may not work exactly as one expects as various days get omitted because part of the data was missing.
(People aged <=18 shouldn’t be using any of this except harmless stuff - where one may have nutritional deficits - like fish oil & vitamin D; melatonin may be especially useful, thanks to the effects of screwed-up school schedules & electronics use on teenagers’ sleep. Changes in effects with age are real - amphetamines’ stimulant effects and modafinil’s histamine-like side-effects come to mind as examples.)

If you’re a coffee or tea drinker, keep sipping: Caffeine may help protect against age-related cognitive decline. “Studies have indicated that caffeine—for example, roughly 500 milligrams daily, the equivalent of about five cups of coffee—may help stave off memory issues in humans,” says Bruce Citron, PhD, a neuroscientist at Bay Pines VA Healthcare System and the USF Morsani College of Medicine in Florida. (Experts warn against taking caffeine supplements, which flood your body with a lot of caffeine all at once.)
To make things more interesting, I think I would like to try randomizing different dosages as well: 12mg, 24mg, and 36mg (1-3 pills); on 5 May 2014, because I wanted to finish up the experiment earlier, I decided to add 2 larger doses of 48 & 60mg (4-5 pills) as options. Then I can include the previous pilot study as 10mg doses, and regress over dose amount.
So with these 8 results in hand, what do I think? Roughly, I was right 5 of the days and wrong 3 of them. If not for the sleep effect on #4, which is - in a way - cheating (one hopes to detect modafinil due to good effects), the ratio would be 5:4 which is awfully close to a coin-flip. Indeed, a scoring rule ranks my performance at almost identical to a coin flip: -5.49 vs -5.5420. (The bright side is that I didn’t do worse than a coin flip: I was at least calibrated.)
Evidence in support of the neuroprotective effects of flavonoids has increased significantly in recent years, although to date much of this evidence has emerged from animal rather than human studies. Nonetheless, with a view to making recommendations for future good practice, we review 15 existing human dietary intervention studies that have examined the effects of particular types of flavonoid on cognitive performance. The studies employed a total of 55 different cognitive tests covering a broad range of cognitive domains. Most studies incorporated at least one measure of executive function/working memory, with nine reporting significant improvements in performance as a function of flavonoid supplementation compared to a control group. However, some domains were overlooked completely (e.g. implicit memory, prospective memory), and for the most part there was little consistency in terms of the particular cognitive tests used making across study comparisons difficult. Furthermore, there was some confusion concerning what aspects of cognitive function particular tests were actually measuring. Overall, while initial results are encouraging, future studies need to pay careful attention when selecting cognitive measures, especially in terms of ensuring that tasks are actually sensitive enough to detect treatment effects.
Last April the scientific journal Nature published the results of an informal online poll asking whether readers attempted to sharpen "their focus, concentration, or memory" by taking drugs such as Ritalin and Provigil, a newer kind of stimulant, known generically as modafinil, which was developed to treat narcolepsy. One in five respondents said they did. A majority of the 1,400 readers who responded said that healthy adults should be permitted to take brain boosters for non-medical reasons, and 69% said that mild side-effects were an acceptable risk. Though a majority said that such drugs should not be made available to children who had no diagnosed medical condition, a third admitted that they would feel pressure to give "smart drugs" to their kids if they learned that other parents were doing so.
Last winter, I spoke again with Alex, the Harvard graduate, and found that, after a break of several months, he had gone back to taking Adderall - a small dose every day. He felt that he was learning to use the drug in a more "disciplined" manner. Now, he said, it was less about staying up late to finish work he should have done earlier, and more "about staying focused on work, which makes me want to work longer hours". What employer would object to that?
I posted a link to the survey on my Google+ account, and inserted the link at the top of all gwern.net pages; 51 people completed all 11 binary choices (most of them coming from North America & Europe), which seems adequate since the 11 questions are all asking the same question, and 561 responses to one question is quite a few. A few different statistical tests seem applicable: a chi-squared test whether there’s a difference between all the answers, a two-sample test on the averages, and most meaningfully, summing up the responses as a single pair of numbers and doing a binomial test:
purpose of this research study titled ‘Nootropics Market – Growth, Future Prospects, and Competitive Analysis, 2016 – 2024’ is to provide investors, developers, company executives and industry participants with in-depth analysis to allow them to take strategic initiatives and decisions related to the prospects in the global nootropics products market.
The body has its own inherent detoxification pathways that are responsible for packaging and removing heavy metals safely from the system. For example, glutathione is known as the body’s ‘master antioxidant’ and aside from playing an important role in preventing free radicals from causing damage to the body’s cells, it also helps to bind to heavy metals and remove them from the body. Research shows that glutathione levels are lower than normal in those on the autism spectrum, so enhancing levels through the diet may be an effective way to prevent the accumulation of heavy metals. Consuming sulfur-rich foods such as broccoli, cabbage, onions, garlic, kale and cauliflower can boost glutathione levels, as well as milk thistle, which has unique flavonoids that also support glutathione production.
During pregnancy and after pregnancy there is often a concern for the potential depletion of the maternal nutrient reservoir due to the needs of the growing foetus. A nutrient that is particularly important for mental wellbeing and is also essential for the growth of the foetus’s brain, is DHA. This is an omega 3 fatty acid that is found in oily fish and is the primary structural component of brain tissue, as well as playing a crucial role in the maintenance of brain cells and neurotransmitter metabolism (our body can also convert plant sources of omegas 3’s into DHA, such as those found in flaxseeds or chia seeds into DHA, but the conversion can often very poor). Deficiency in this nutrient during pregnancy is common, namely because of lack of seafood intake (the most bioavailable source of DHA) due to poor eating habits and concerns of mercury levels in fish during pregnancy, as well as higher requirements during foetal growth, which can lead to depletion. Due to the role that DHA plays in neurotransmitter metabolism, deficiency in this nutrient has been correlated to symptoms of depression during pregnancy (7). In order, to support your intake of omega 3, aim to have 3 portions of oily fish a week from sources that are low in mercury. These are mainly small fish that have a short life-span such as sardines, mackerel and herring. If you are vegetarian or vegan, although omega 3 is less readily available, it is still possible to get this nutrient from your diet through flax seeds, chia seeds, walnuts and seaweed. If you feel you may not be getting enough through your diet, you may want to consider using a good quality fish oil supplement (or algae based supplement if vegan) as an option. With fish oils, aim to choose a supplement that has been filtered for heavy metals and other pollutants to make sure you're getting the full benefits of the omega 3 oils.
the rise of IP scofflaw countries which enable the manufacture of known drugs: India does not respect the modafinil patents, enabling the cheap generics we all use, and Chinese piracetam manufacturers don’t give a damn about the FDA’s chilling-effect moves in the US. If there were no Indian or Chinese manufacturers, where would we get our modafinil? Buy them from pharmacies at $10 a pill or worse? It might be worthwhile, but think of the chilling effect on new users.
One curious thing that leaps out looking at the graphs is that the estimated underlying standard deviations differ: the nicotine days have a strikingly large standard deviation, indicating greater variability in scores - both higher and lower, since the means weren’t very different. The difference in standard deviations is just 6.6% below 0, so the difference almost reaches our usual frequentist levels of confidence too, which we can verify by testing:
The soft gels are very small; one needs to be a bit careful - Vitamin D is fat-soluble and overdose starts in the range of 70,000 IU36, so it would take at least 14 pills, and it’s unclear where problems start with chronic use. Vitamin D, like many supplements, follows a U-shaped response curve (see also Melamed et al 2008 and Durup et al 2012) - too much can be quite as bad as too little. Too little, though, is likely very bad. The previously cited studies with high acute doses worked out to <1,000 IU a day, so they may reassure us about the risks of a large acute dose but not tell us much about smaller chronic doses; the mortality increases due to too-high blood levels begin at ~140nmol/l and reading anecdotes online suggest that 5k IU daily doses tend to put people well below that (around 70-100nmol/l). I probably should get a blood test to be sure, but I have something of a needle phobia.
Sun: This is a day I devote to spiritual disciplines and deep personal exploration, along with a hefty dose of neurogenesis, and for a day such as this, I’ll use a more potent neuron sprouting and ego-dissolving mix – most notably a blend of psilocybin microdose with Lion’s Mane extract and niacin (if the skin flush and increased blood flow from niacin tends to be too much for you, you can also use “nicotinamide riboside”, a form of vitamin B3 that has similar effects without the flushing).
Tempted to skip breakfast? Studies have found that eating breakfast may improve short-term memory and attention. Students who eat it tend to perform better than those who don’t. Foods at the top of researchers' brain-fuel list include high-fiber whole grains, dairy, and fruits. Just don't overeat; researchers also found high-calorie breakfasts appear to hinder concentration.

Compared with those reporting no use, subjects drinking >4 cups/day of decaffeinated coffee were at increased risk of RA [rheumatoid arthritis] (RR 2.58, 95% CI 1.63-4.06). In contrast, women consuming >3 cups/day of tea displayed a decreased risk of RA (RR 0.39, 95% CI 0.16-0.97) compared with women who never drank tea. Caffeinated coffee and daily caffeine intake were not associated with the development of RA.
Ampakines bind to AMPARs to block uptake of glutamate, thereby increasing synaptic responses, and this has indeed been shown to minimize the effects of conditions such as Alzheimer’s. Ampakines are also being studied as possible treatments for schizophrenia, depression, ADHD and more. But there is a huge risk associated with ampakine consumption. They are now tightly regulated because if you exceed a safe dosage, you will begin to suffer neuronal damage from glutamate toxicity, which leads to some of the very conditions that ampakines are thought to attenuate. Ampakine consumption can also lead to a decrease in long-term synaptic depression (LTD), a process by which specific synapses (the space between neurons across which information is sent) are intentionally weakened in order to avoid a plateau in the efficiency of your synapses. In other words, it allows your neurons and their connections to continue growing in efficiency. LTD is believed to be necessary for healthy synaptic plasticity (the adaptability of synapses), memory function and motor skills. To be honest, there is debate over whether cognitive functions like motor learning are truly dependent upon LTD, but it is possible that if you were to take a higher-than-recommended dose of an ampakine, the overstimulation that would result may lead to suppressed LTD and consequently to poor memory and motor function.
This calculation - reaping only \frac{7}{9} of the naive expectation - gives one pause. How serious is the sleep rebound? In another article, I point to a mice study that sleep deficits can take 28 days to repay. What if the gain from modafinil is entirely wiped out by repayment and all it did was defer sleep? Would that render modafinil a waste of money? Perhaps. Thinking on it, I believe deferring sleep is of some value, but I cannot decide whether it is a net profit.
Caffeine, Tulsi and Astragalus: Tulsi is one of the greatest calming adaptogens that exists, trusted and revered for centuries in Ayurvedic medicine and culture. Tulsi has been researched and shown to uplift mood, support digestion, and promote balanced energy. Because it’s also an anxiolytic (causes anti-anxiety effects) tulsi, similar to coffee with L-theanine, does a good job balancing out any over-stimulating effects of the caffeine in coffee. But you can also take things one step further and blend in astragalus, which, in Chinese medicine, is considered a “strong” Ki invigorating herb that provides a stable source of non-crashing energy. Astragalus also contains an enormous variety of saponins, flavonoids, and polysaccharides, and is considered to be a “longevity adaptogen”. Pairing with antioxidant-rich coffee and tulsi produces a match made in longevity heaven. For this blend, which I often use if drinking coffee in the afternoon, I’m a fan of the Four Sigmatic Adaptogen Blend, which contains coffee, astragalus, tulsi and cinnamon.
I’ve been taking nootropics on and off for a month, and despite my spurts of productivity, I’m still not 100 percent sure that they’re working. I could well be placebo-ing myself into thinking I'm working harder and focusing better than I typically do. But apparently enough people are feeling some effect, placebo or not, because nootropics start-ups are thriving. There’s truBrain, Nootrobrain, Nootroo, and a host of others. Nootrobox, the company that makes my pills, says that it’s selling "five figures" worth of cognitive supplements monthly to customers that include top Silicon Valley executives and Hollywood moguls.
It doesn't take a neuroscientist with a degree in nutrition to get that diet can affect the brain. It does take a neuroscientist with a degree in nutrition to provide such a smart research-driven analysis of how and to what extent. Brain Food is based on the work of literally hundreds of scientists and provides a dietary roadmap to enhanced cognitive power. That Dr. Mosconi's book is also fully accessible to a layperson makes this a true must read. (Bonus: Chapter 16 is a mini-cookbook with "brain boosting" recipes including several that are kid-friendly.)
I do recommend a few things, like modafinil or melatonin, to many adults, albeit with misgivings about any attempt to generalize like that. (It’s also often a good idea to get powders, see the appendix.) Some of those people are helped; some have told me that they tried and the suggestion did little or nothing. I view nootropics as akin to a biological lottery; one good discovery pays for all. I forge on in the hopes of further striking gold in my particular biology. Your mileage will vary. All you have to do, all you can do is to just try it. Most of my experiences were in my 20s as a right-handed 5’11 white male weighing 190-220lbs, fitness varying over time from not-so-fit to fairly fit. In rough order of personal effectiveness weighted by costs+side-effects, I rank them as follows:
“We stumbled upon fasting as a way to optimize cognition and make yourself into a more efficient human being,” says Manuel Lam, an internal medicine physician who advises Nootrobox on clinical issues. He and members of the company’s executive team have implanted glucose monitors in their arms — not because they fear diabetes but because they wish to track the real-time effect of the foods they eat.
One thing I did do was piggyback on my Noopept self-experiment: I blinded & randomized the Noopept for a real experiment, but simply made sure to vary the Magtein without worrying about blinding or randomizing it. (The powder is quite bulky.) The correlation the experiment turned in was a odds-ratio of 1.9; interesting and in the right direction (higher is better), but since the magnesium part wasn’t random or blind, not a causal result.
More than once I have seen results indicating that high-IQ types benefit the least from random nootropics; nutritional deficits are the premier example, because high-IQ types almost by definition suffer from no major deficiencies like iodine. But a stimulant modafinil may be another such nootropic (see Cognitive effects of modafinil in student volunteers may depend on IQ, Randall et al 2005), which mentions:
Cocoa flavanols (CF) positively influence physiological processes in ways which suggest that their consumption may improve aspects of cognitive function. This study investigated the acute cognitive and subjective effects of CF consumption during sustained mental demand. In this randomized, controlled, double-blinded, balanced, three period crossover trial 30 healthy adults consumed drinks containing 520 mg, 994 mg CF and a matched control, with a 3-day washout between drinks. Assessments included the state anxiety inventory and repeated 10-min cycles of a Cognitive Demand Battery comprising of two serial subtraction tasks (Serial Threes and Serial Sevens), a Rapid Visual Information Processing (RVIP) task and a mental fatigue scale, over the course of 1 h. Consumption of both 520 mg and 994 mg CF significantly improved Serial Threes performance. The 994 mg CF beverage significantly speeded RVIP responses but also resulted in more errors during Serial Sevens. Increases in self-reported mental fatigue were significantly attenuated by the consumption of the 520 mg CF beverage only. This is the first report of acute cognitive improvements following CF consumption in healthy adults. While the mechanisms underlying the effects are unknown they may be related to known effects of CF on endothelial function and blood flow.
Christopher, love your heart for Pete’s security in who he is to The Lord. So cool. Brother, God does judge. Jesus is even referred to as “the righteous judge” (2 Timothy 4:8). In the first 5 verses of Romans 2, the judgment of God is even mentioned 3 times. Matthew 25:46 speaks of what will happen when God judges – that some “will go away into eternal punishment, but the righteous into eternal life.” Those who believe in Jesus Christ as their Lord and Savior who died for their sins and rose again will be and are “by grace… saved through faith” (Ephesians 2:8-9) in Jesus as such, having their sins forgiven and the righteousness of Jesus credited to them. (Romans 4:22-25) Thank you, Lord!
The use of cognition-enhancing drugs by healthy individuals in the absence of a medical indication spans numerous controversial issues, including the ethics and fairness of their use, concerns over adverse effects, and the diversion of prescription drugs for nonmedical uses, among others.[1][2] Nonetheless, the international sales of cognition-enhancing supplements exceeded US$1 billion in 2015 when global demand for these compounds grew.[3]
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